Umformtechnologie: Prozesse – Werkstoff‐ charakterisierung – Simulation – Verifikation

Sheet forming technology – processes, materials, simulation and verification Hydroforming and Deep Drawing represent leading technologies for forming sheet metal components. The Materials Branch of the University of Duisburg‐Essen works since more than 10 years in the field of Hydroforming and showed that Hydroforming increases the strength and that the weldings of hydroformed tubes normally exhibit a same (fatigue) strength as the base material. For an improvement of the economics of hydroforming spliced tubes were considered and standard hollow nodes for tubes nodes structures were developed and a proposal was made to produce these tubes in variable tools with segments or lamellas. A significant increase in economics of Hydroforming and of Deep Drawing of components is achieved by an introduction of the principles of an integral (cooperative) development of products. At the University of Duisburg‐Essen the following stages are run through: CAD (the Material Branch uses PRO/ENGINEER®), forming simulation – for that PAM‐STAMP® (ESI) and PATRAN MARC MENTAT® (MSC) are used – FEM strength calculation and EVICD for a consideration of variable service loading. Forming simulation needs as basic material data the yield curve, the parameters of anisotropy and the Forming Limit Curve (FLC). For a determination of the FLC in Deep Drawing Tests suitable Nakazima specimens were developed by applying the principles of cooperative product development. The specimens could then successfully be validated in Deep Drawing Tests, which were instrumented by the advanced 3D‐forming‐analysis‐system AUTOGRID inProcess (VIALUX). Various other forming simulations were also performed and some general rules for the performance of forming simulations were formulated. Finally, reverse engineering is briefly discussed.     

Hochpolymere Werkstoffe. Aufbau – Eigenschaftsbild – Anwendung

High Polymers: Structure — Properties — Application . The close relationship between the Institute of Materials Technology and the State Institute of Materials Testing gives an informal and continual active exchange of research on materials, materials testing and education. A special correlation in the field of high polymers was reached. Outstanding examples from the important research work over a period of the last five years have been singled out, and the development of the subjects the extent of the problems involved, the complexity and the results of the subject have been outlined. It is here, chiefly a matter of investigation of the relationship between the structure or duro-plastic multicomponent systems, the dependence of molecular orientation and electrostatic charge of thermoplastic plastic materials on the conditions of processing, as well as those of the question of the properties of the components of Duro- and Thermoplastics. The research work which had been planned and begun concentrated as usual on the related applications, the reasonableness of engineering processes involved in the range — row-stuff and the end-product. It is, however, readily recognizable, that the interdisciplinary collaboration in these tasks will be intensified in the future.     

Modelle zur Parameteroptimierung von Timed Token Rotation-Protokollen

Zusammenfassung In dieser Arbeit werden Modelle zur Verfügung gestellt, mit deren Hilfe es möglich ist, Parameteroptimierungen von Timed Token Rotation Protokoll-Systemen vorzunehmen. Die zu optimierenden Parameter sind dabei die Wartezeit einer (mehrerer) Station(en) bzw. der Durchsatz. Grundlage dieser Modelle sind einerseits analytisch-heuristisch gewonnene Wartezeitapproximationen, die mittels Simulation validiert wurden, und andererseits moderne Methoden der nichtlinearen Optimierung. Die Wartezeitapproximationsformel stellt jeweils die zu minimierende Zielfunktion dar, wobei die Forderungen des Anwenders, die bei der Suche eines Optimums einzuhalten sind, in Form von Nebenbedingungen (hier: Ungleichungen) berücksichtigt werden. Es werden monokriterielle Verfahren, bei denen nur das Kriterium Wartezeit zur Diskussion steht, und bikriterielle Verfahren vorgestellt, deren Ziel darin besteht, sowohl die Wartezeit zu minimieren als auch den Durchsatz zu maximieren. Schließlich werden die vorgestellten Optimierungsmodelle an Beispielen demonstriert.